Continuous automatic ore assay system



June 30, 1964 A. s. HENDERSON ETAL 3,139,578

CONTINUOUS AUTOMATIC ORE ASSAY SYSTEM Filed Dec. 1, 1959 4 Sheets-Sheet l INVENTORJ. Raw/4mm 6. HAM/MASON Jeri/v 17. R1505 June 1954 A. s. HENDERSON ETAL 3,139,578

CONTINUOUS AUTOMATIC om: ASSAY SYSTEM 4 Sheets-Sheet 2 Filed Dec. 1, 1959 June 30, 1964 A. S. HENDERSON ETAL CONTINUOUS AUTOMATIC ORE ASSAY SYSTEM To Ca wvrew M01 6 75 VINE //6 VI V2 I a, u

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June 30, 1964 A. s. HENDERSON ETAL ,139,578

CONTINUOUS AUTOMATIC ORE ASSAY SYSTEM Filed Dec. 1, 1959 4 Sheets-Sheet 4 &

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United States Patent F 3,139,578 CONTIVUOUS AUTOMATIC ORE ASSAY SYSTEM Ashland S. Henderson, Palo Alto, Caliii, and John R. Riede, White Bear Lake, Minn, assignors to Reserve Mining Company, Silver Bay,,Minn., a corporation of Minnesota 7 Filed Dec. 1, 1959, Ser. No. 856,584 28 Claims. (Cl. 324-34) This invention relates to an improved method for automatically obtaining the assay of a crude magnetite ore on a moving conveyor belt, on a continuous and integrating basis. In the following'description we will discuss the invention with reference to the beneficiation of taconite.

Taconite or low grade iron ore, as found in the mine, varies in magnetic iron content. It has been found advantageous'to the crushing and beneficiating process of taconite ore to know the magnetic iron content of the material as it leaves the mine or before it reaches the beneficiating plant.

By using the system nowto be described it is possible to automatically obtain an instantaneous and integrated assay ofthe ore as it passes over the first conveyor belt after being delivered from the mine and immediately after the second coarse crushing stage.

It has been found advantageous in the 'beneficiating of taconite ore to maintain'a constant magnetic iron content material to the beneficiating plant for optimum performance.

With this invention providing an instantaneous and integrated assay of the ore, delivery of a material of a uniform magnetic iron content can be accomplished by mixing or blending of the different grade ores. This assay information allows adjustment of the mine operation, by shovel movement, for it is possible to attain the individual assay of truckloads of ore from known locations to detera mine which ore piles should be used to blend the ore to a desired grade. Because of the surge capacity in the storage bins between the mine and the mill, this assay enables the beneficiating plant to predict in advance (24- 48 hours) the grade or ore which will be milled. The primary object of the present invention is to determine the mine assay data at an early enough time to control the ore characteristics, and render the ore: substantially uniform, rather than 24 to 48 hours later.

This invention has the following additional advantages, each of which constitutes an object of the present invention:

(1) It continuously monitors both the amount of magnetic iron and the total weight of ore passing over acouveyor.

recorded, it is possible to determine 'just what the assay of the orefrom any mine location is running. By pushing a read out button it ispossible to read and automatically record the average ore assay over an elapsed time. t This elapsed time and the total tonnage that passed over theconveyor both appear on a read on -panel. The system is so programmed that once eacheight or more hours it will automatically record the average asi say for that period and reset the system so that the average assay isrecorded forv each subsequent pre-set period.

, 3,139,578 Patented June 30, 1964 Referring now to FIG. 1 the system basically consists of a coil 20 (FIG. 1) sensing the amount of magnetic iron on the conveyor belt and a conveyor scale consisting of sensing idlers 21 and 22 measuring the total weight of ore on the conveyor belt. The coil is located at the exact point on the conveyor where the scale weighing is performed, andby so locating these different sensing devices, time delay problems are eliminated.

Still referring to FIG. 1, the coil 20 feeds the converter 23 which converts the coil output signal, which is proportional to magnetic iron, into a useable proportional voltage.

This voltage is fed into a recorder 24 which records, integrates, and totalizes on a totalizer 203, the total magnetic iron which is carried by the conveyor. Inaddition to this, the recorder is equipped with a retransmitting slidewire which transmits a signal to the ratio recorder 26, which signal is proportional to the magnetic iron on the conveyor. It is also equipped with a device that sends one electrical pulse for each magnetic ton to the read out control station.

The scale load cell 27 sensing the pounds per foot on idlers 21 and 22, and a transmitting selsyn 28, driven from tail pulley 29, measuring the feet per minute, send the necessary signals to the scale indicator 30, and totalizer 178. The total weight indicator and totalizer is also equipped with a retransmitting slidewire and pulse unit which sends the total weight information to the ratio recorder and read out control station.

The read out control station 32, as previously mentioned, receives one electrical pulse for each magnetic ton, and one electrical pulse for each gross weight ton passing over the conveyor. It continuously adds and stores these pulses in analog form so that after any elapsed time the analog of the total magnetic tons and the analog of the total tons may be fed into the ratio recorder 26, I

where the analog of the magnetic tons is divided by the I analog of the total tons and the resultant figure is the percent magnetic iron. v

The read out station 32 in general operates as follows: Each time a pulse is received from the magnetic iron integrator, a multiturn potentiometer is moved a fixed amount. This in effect stores the total magnetic tons. Each time it receives a pulse from the total weight integrator, it stores it in another potentiometer and it also steps the total weight counter on the read out control panel one unit, usually a ton. Thus it stores total magnetictons in an analog device, the potentiometer,

and it stores the total weight tons in both analog and digital forms. Since the storage potentiometers can store only a limited amount of tons, they must be reset after a certain period of time. In order to make certain that this resetting action will be done, the device is equipped with a time programmer 34 which will automatically reset the device aftera predetermined period of time.

The ratio recorder is calibrated to read directly in percenti'magnetic iron. 1 5 i 1 5 Referring now to the read out, station 32 it may be seen that there are two push buttons, one 35 to read and the other 36 to reset. pressed, the ratio recorder 26 is continuously recording the instantaneous percent magnetic iron moving on the conveyor belt and the total weight counter 31 on the read out panel is totalizing the total weight. The time indicator is indicating the elapsed time since the device was reset. The read button 35, being depressed, momen tarily disconnects the ratio recorder 26 or percent magnetic ironrecorder from the instantaneous assay function and connects it to the stored information in the read out panel. The ratio recorder would then indicate and record the average assay since the device has been reset When the read button is returned to its normal position, the system automatically starts recording continuous When neither button is being 7 assay again, without having alfected any of the stored information in any way. Thus it may be seen that aver age assay readings, since the last reset period, may be taken at any time without disturbance of the system.

When the predetermined time has elapsed and the system is reset, the total weight counter and the elapsed time indicator both return to zero and immediately start their normal programming cycle. The ratio or percent magnetic iron recorder however is automatically disconnected from the instantaneous assay function and connected to the stored or average assay circuit. It stays connected to this circuit for about ten minutes and is then reconnected to the instantaneous assay function. This ten minute delay while averaging is programmed into the device to make certain that the average assay reading may be easily distinguished from the instantaneous assay readings on the chart.

. The reset switch 36 (FIG. 1) when closed permits the system to go through normal read out and reset without waiting for it to time out automatically.

The objects and advantages of this invention will be apparent in the following detailed description of one embodiment of the invention in conjunction with the accompanying drawings in which FIG. 1 is a block diagram showing the main elements of the invention;

FIG. 2 is an electrical wiring diagram showing the operative relationship of the various electrical elements of the system;

FIG. 3 is a detailed wiring diagram of a measuring circuit;

FIG. 4 is a detailed wiring diagram of an amplifier;

- FIG. 5 is a detailed wiring diagram of an oscillator amplifier.

The Magnetic Material Sensing Device All points labeled L and L in the drawings indicate 117 volts A.C. Referring now to the electrical circuits and members associated therewith we show, in the upper left portion of FIG. 2, the sensing means for quantitatively determining the amount of magnetic material moving in a path past the induction couple consisting of primary coil P, and two secondary coils S and S which in a structural assembly are axially spaced one on each side of the primary. A conveyor 36 (FIG. 1) passes axially through the couple, and any magnetic material thereon increases the induced current in secondary coils S S An A.C. current from L L feeds into a constant voltage transformer 40 through a resistor 41 into primary P. One side is grounded at 42. The voltage developed in coils S S is proportional to the quantity of magnetic material on conveyor 36.

The A.C. current flowing in the secondary circuit is rectified by diode 43 so that the DC voltage drop across resistor 44 is proportional to the aforesaid amount of magnetic material. It is necessary to make an operating correction for extraneous effects in the operating circuit other than those resulting from passage of the magnetic concentrate on the conveyor. This correction is effected by taking an adjustable part of the transformer output through a phasing capacitance 45 and a variable resistor 46. In essence, the object is to vary resistor 46 to produce at diode 48 a voltage equivalent to that at diode 43 when the circuits are energized but no magnetic material is passing on the conveyor. Uunder these conditions the DC. voltage across resistor 44 is equal and opposite to the D0. balancing voltage across resistor 49 with no magnetic material passing.

A variable resistor 52 and coupled capacitors 53 and 53a act as a matched resistance-capacitance circuit to dampen the signal developed by passage of magnetic material.

Variable resistor 52 is provided to modify the signal voltage at points 54, 55, so that a signal of predetermined potential can be fed to'the subsequent circuit elements.

The Measuring Circuit The signal from points 54, 55, is shown in FIG. 2 as being delivered in succession to two units, consisting respectively of a measuring circuit and an amplifier, these items being incorporated in the blocks marked respectively 56 and 57 in FIG. 2. The measuring circuit is shown in greater detail in FIG. 3 and a suitable amplifier in FIG. 4.

Referring now to FIG. 3, the points 54 and 55 on FIG. 2 may be indicated as the input points similarly identified at the bottom of FIG. 3. In the circuit of FIG. 3, as will directly appear, we have provided a battery-balanced resistance bridge. The battery is periodically checked against a commercially obtainable laboratory standard cell which, when used only as an occasional check means, remains at constant value for a long period. We have provided a multiple throw switch 56 shown in a normal position which can be manually thrown to a check position at selected intervals, but which normally is in the opposite or running position.

At the signal input point there is a resistor-capacitor alternating circuit consisting of resistor 57 and a capacitor 58. Switch 56 is in the upper or normal operating position, which places resistor 57 in electric circuit communication with point 59 through lines 60 and 61.

The upper part of FIG. 3 constitutes a balancing bridge of the wheatstone general type, in which points 62, 59, 63 and the intermediate resistors 64 and 65 form a lower arm, and points 62, 68, 69 and 63, and the intermediate resistors 70, 71, and the parallel resistor assembly 72, 73 and 74 form the upper arm. The intermediate cross arm 62, 75, 63, contains the battery 76 and a variable resistor 77. In the parallel resistor bank 72, 73, 74, is a variable element 74a for balancing purposes.

Battery 76 supplies a constant voltage between points 62 and 63. This voltage is arranged to be of opposite polarity to the signal being measured. With the switch still in the upper position the incoming signal to be measured proceeds from point 54 through lines 60 and 61 to point 59, and from point 55 through the amplifier (connected at points 78 and 79) and then through lines 82 and 83 to point 78. Signal voltage at the terminal points 59 and 78 therefore is disposed, by means of the measuring bridge above described, to be opposed in polarity to the voltage of battery 76. The amplifier, to be more fully described in connection with FIG. 4, is in series with terminals 78 and 79, and is connected to measure and amplify any difference between the established battery voltage and the fluctuations in the incoming signal at 54, 55, coming from the induction couple heretofore described.

The amplified current energizes a motor 84, FIGS. 2 and 3, as will appear. It may now be stated that the function of motor 84 is to operate the sliding contact 74a on resistor 74 (FIG. 3) to a position such that the voltage produced by battery 76 across points 59 and 79 is equal and opposite to the incoming signal at 54, 55.

It is apparent that when the signal is thus balanced there will be no output signal at points 78 and 79, which will in turn leave no potential to be amplified and consequently motor 84 (FIG. 2) will stop. Motion of the motor to the stop position, however, will have made the necessary adjustments in the further controlled elements to achieve the results desired.

To assure a proper balancing voltage output from battery 76 (FIG. 3) it is occasionally checked against a standard cell 85, as follows. Manual switch 56 is moved down to its checking position, during which movement a clutch mechanism shown as a broken line in FIG. 3 simultaneously connects the slider on resistor 77 with motor 84 (FIGS. 2 and 3).

I With the switch in the down or check position the voltage originating in battery 76 and developed across resistor 65 is compared with the voltage of standard cell 85 and impressed between points 86 and 87. Since the signal voltage at terminals 54 and 55 has been disconnected by moving switch 56 to the check position, the amplifier will now amplify a differential impressed across resistor 88, the amplifier circuit proceeding from terminal 79 through lines 82, 90,'resistor 88, andlines 91 and 92 to terminal 78. Any detectable potential difference between the battery 76 and standard cell 85 will be amplified by the amplifier which will cause motor 84 to move and to operate the sliding contact on variable resistor 77 so as to cause thebattery voltage across resistor 65 to balance the, standard cell voltage by making the .two

voltages equal and opposite. This will periodically check and adjust the battery voltage and insure accurate measuring of the incoming signal at 54, 55. Switch 56 is of course returned to the upper or normal operating position after each check.

a The Amplifier Proceeding from terminal points 78 and 79 of FIG. 3 we arrive at the similarly identified terminal points at the left side of the amplifier diagram'(FIG. 4). This shows a conventional D.C. amplifier which takes the low potential signal coming in at 78, 79 and amplifiesit sufficiently to energize balancing motor 84 (FIGS. 2 and. 3). As has been seen, the balancing motor operates to return the energizing voltage to a zero value. As heretofore intimated, as long as the voltage at terminals 54, 55 (FIG. 3) is constant no potential difference is detected at terminals 78, 79. The position to which motor 84 moves to achieve this balance is then representative of the signal impressed at the points 54, 55.

In FIG. 4 any unbalance of the measuring circuit is effective at terminal points'78 and. 79 and is converted to alternating current by input transformer 95 and converter 96 and shaped bythe matched resistor-capacitor elements 97 and 98. The alternating current signal is .6 t p I The Vane Oscillator Integrator Referring to FIG. 2, synchronous scanning motor 113 drives earn 114 at a rate of 6 rpm. Rotation of this cam causes scanningarm 115 to sweep a constant arc.

. The coils 116 mounted on scanning arm 115 detect the the vane 106 lies directly in the path of coils 116, its 7 position, and hence the balance motor position, is sensed twice each revolution of the cam. The sensing coils are in the circuit of anelectronic modified Hartley oscillator shown in detail in FIG. 5 and explained hereinafter, and

then fedto two voltage amplifying 1'2AX7 tubes 99 and 100 in tandem relationship, and thereafter the output from tubes 99 and 100 is delivered to the grids of two 12AU7 tubes 105 and 106 in parallel. 5

The' Balancing Motor (FIG. 2) which responds to amplifier'57 is as follows.

The motor operates:

3)(A) The moving slider on battery rheostat 77 (FIG. (B) The sliding contactor 74a (FIG.;3); u (C) A re-transmitting slidewire contactor 103 moving on slidewire 104 (FIG. 2); I

(D) An instrument pointer and pen 105 (FIG. 2) indicating, recording and totalizing the flow of dry magnetic material moving on conveyor 36 (FIG. 1);

(E) The vane assembly 106 (FIG.;2) of a conventional moving vane-oscillator type integrator.

The linkages for the operation of these various devices are indicated by broken lines leading fromzmotor 84 (FIG. 2) and on FIG. 3 for rheostats 77 and 74.

The sources of constant voltage for retransmitting slidewires 104 and 109 and storage devices 110 and 111 (FIG. 2) are numbered identically since they are similar- The operation of these power supplies will be explained later. g

The vane-oscillator type integrator is very'common to the trade, and a detailed circuit description is not neces-' sary. Its operation and use in this invention will be readily understoodafter the'following brief explanation.

functions as an on-oif switch for the counter motor C. Oscillator operation depends upon the position of the vane with respect to the coils. When the vane is between the coils, oscillation ceases, a relay closes and the counter motor C drives the counter at a constant speed. As the coils move away from the vane, oscillation begins again, the relay opens, and counting ceases.

The Brake Circuit A brake circuit is provided for the counter motor to in-' sure against possible coasting of the counter after the coils move out of the field of the vane.

Referring now to FIGURE 5, we find the brake circuit B, the oscillator and its associated relay and a centrifugal switch S the purpose of which will be explained. The correct voltages necessaryfor oscillator, relay coil RC operation and duo triode tube labeled V and V are supplied by transformer T secondary windings. The primary is energized by 117v. A.C. tube V plus associated components C C C C R 120, 121, and vane coils 116 (FIG. 2) make up the oscillator section. Adjustablecapacitor C coil 121, and the vanecoils make upthe frequency determining circuit. The feed back required to sustain oscillations is accomplished mainly by capacitor C When the vane passes between the two vane coils the inductance is changed to such an extent that oscillation ceases. Variable capacitor C adjusts the sensitivity of the oscillator so that the leading edge of the vane starts and stops oscillating when in the center of the coils. This is necessary since the vane passes through the coils in both directions.

During oscillation, tube V bias is so negative that there is no plate current flow, therefore relay coil RC remains tie-energized. As soon as oscillation ceases, the bias is such that plate circuit becomes conductive, and current will flow through relay coil RC thereby energizing it. Energizing RC causes contacts RC to close and normally closed contacts RC to open which causes synchronous counterrnotor C to run.

Since themotor will coast a small amount when the energizing power is removed, the brake circuit consisting of capacitor C resistor R and selenium rectifier S 'is provided to brake the counter motor. When relay coil RC is de-energized, contacts RC close and RC opens'which in turn feeds a filtered half wave voltage to counteract the voltagecreated by the collapsing l'lcid of the counter motor windings. This is, in effect, a form of dynamic braking.

Since conveyor 36 (FIG. 1) is sometimes stopped with stray magnetic material on the belt and within the coil field, centrifugal'switch S is made responsive to operation of the conveyor motor so as to break the counter motor circuit when the conveyor is at a, standstill.

The Gross Weight Sensing Means strain gauge, or load cell 27 is suspended from the conveyor bed and supports scale carriage 122. Material being conveyed over idlers 21 and 22 creates a downward force on the scale carriage and hence results in compression of the strain gauge. This in turn produces an electrical signal proportional to the amount of compression. Although the conveyor drive motor is a constant speed device, compensation for a varying belt speed is taken into consideration by providing a transmitting selsyn 28 driven from tail pulley. This selsyn drives a receiving selsyn located in instrument 124 and as will be seen later, compensates mechanically for changes in belt speed.

Referring to FIG. 2, broken line box 125 contains the electrical components of the resistance type load cell. The cell contains a set of electrical strain gauges bonded to a metal post which carries the material weight. As the strain gauges are compressed in loading the gauge wires vary in electrical resistance in proportion to the belt loading. As can be seen from the diagram, strain gauges 126 through 129 make up a bridge circuit. Since resistance is afiected by temperature changes, temperature compensating resistors 130 and 131 are added in series with the bridge input voltage.

The load cell D.C. input voltage is developed by a bridge rectifier type power supply shown in broken line box 132 in FIG. 2. Bridge rectifiers 134, fed from step down transformer 135, provides full Wave rectification. Resistors 136 and 137 are voltage dropping resistors and are used to provide the cell with the correct voltage. Capacitor 138 serves as a filter.

The components shown in broken line box 139 make up a combination measuring and calibrating circuit. The load cell output passes through series resistors 140 through 145 and a bridge circuit composed of resistors 148 through 152. Potentiometer 142 provides a means of zeroing the system with no load on the scale and bridge output potentiometer 151 provides a means of calibrating the instrument with a known weight on the scale-the voltage fed from junction of resistors 153 and 154 and feeding to junction between resistors 144 and 145 provide correct compensation for resistance of cell input leads plus providing temperature compensation for the load cell. The output of this measuring circuit is fed at points 155 and 156 into a conventional D.C. amplifier 57a as described previously, an identical one being shown at 57 in FIG. 4. This incoming signal, greatly ampli tied, energizes the winding 157 of motor 158, the phase of which determines the direction of the motors rotation. This motor 158 in turn moves a contactor on resistor 152 which permits the system to achieve a balance. The motor will drive the contactor until there is no signal at points 155 and 156.

Balance motor 158 also drives, through mechanical linkages:

(1) A contactor 159 on resistor 160 which varies the voltage to an instrument indicator 161 calibrated in tons per hour. The voltage necessary for this circuit is provided by a battery 162. The variable resistor 163 provides the means for calibrating the indicator by varying the current through it.

(2) A re-transrnitting slidewire contactor 164 which makes up part of the ratio circuit that feeds amplifier 165 (right end of FIG. 2) and hence the indicator 26 showing the percent magnetic iron. The use of this slidewire will be explained later on in this circuit description.

(3) The ball assembly 167 in a ball and disc type integrator shown in broken line box 168. The operation of this, together with the selsyns, will be explained next.

The transmitting selsyn 28 (FIGS. 1 and 2) as explained previously, and driven by tail pulley 29 (FIG. 1) drives the receiving selsyn 169. The primary windings 170 and 171 are in parallel and fed from 117 V. AC. line. The voltage developed by a specific angular movement of windings 174 in the transmitting selsyn 28 will cause windings 175, which comprise the rotor of the receiving selsyn, to rotate the same angular movement and in the same direction. In this case, the transmitter 28 is driven at a speed proportional to the speed of the tail pulley 29. This continuous, but not necessarily constant, rotation causes the receiving selsyn 169 to rotate at the same r.p.m. The receiving selsyn rotor is mechanically linked to the disc 176 and causes rotation thereof as indicated by an arrow. The energy is transferred from the rotating disc to the shaft 177 through the use of the ball assembly. As explained previously, balance motor 158 drives the ball assembly. The direction of movement is indicated by arrows and the limit of travel is from the center of the disc to the outside edge. No transfer of energy will occur with the balls in the center and as can be seen from the drawing, the r.p.m. of shaft 177 is maximum with the balls riding on the outside rim of the disc. The shaft 177 in turn is coupled to counter 178 which is digitally indicating gross long tons per hour. To summarize the operation of the continuous ball and disc integrator at this point: Balance motor 158 movement is proportional to the downward force on idlers 21 and 22 in FIG. 1. The greater the force, the greater the movement of the motor in one direction. As the downward force increases, the ball assembly is moved towards the outside rim of the disc 176 causing the shaft 177 to drive counter 178 at a greater speed. The counter will hence indicate more gross tons for a given time.

Voltages feeding slidewires 104 and 109, and storage devices and 111 (all in FIG. 2) are developed by a conventional DC. current regulated power supply shown in broken line box 173 at the top center, FIG. 2, and 173a at the bottom center.

The operation is as follows: Step down transformer 179 transforms line voltage L and L to a low voltage suitablefor this type of operation. The A0. is rectified by diode 180 and a special current regulating diode 181. The pulsating DC). is then filtered by capacitor 182 and the voltage further decreased by the drop across resistor 183 and rheostat 184. Rheostat 184 through the use of sliding contactor 185 is provided to vary the output voltage so that a signal of predetermined potential can be fed to subsequent circuit elements.

Reading and Recording Percent Magnetic Iron Indicator 26 (FIG. 1) is continuously indicating and recording the percent magnetic iron on conveyor 36. Since the flow of material is intermittent on this conveyor, the chart pattern is such that an accurate reading cannot be obtained. For this reason, two devices are provided that will enable this equipment to give an accurate readmg.

One is a read out switch 35 (FIG. 1) which may be actuated at any time. This connects the ratio circuit with storage devices which have stored the accumulated magnetic and gross tonnages. The ratio circuit is adjusted by the use of rheostats in the power supplies so that the proper division is performed and the instrument indicates percent magnetic iron. During the time that the read out switch is depressed, the variable field signals coming from scale 27 and induction coil 20 (FIG. 1) are disconnected, hence a steady signal from the storage devices is fed into the ratio circuit and then into the instrument which permits an accurate reading to be obtained.

The other method of connecting the storage devices into the ratio instrument to obtain an accumulative percent magnetic iron reading is similar to above except that it is,,done automatically through the .use of timer 34 (FIG. "1) and an'associated switch. A predetermined interval between readouts is set up on the timer,the duration of which is limited mechanically by the capacity of the storage devices. When the device is automatically timed out, the storage devices and counter are returned to their zero position and the cycle begins again.

A detailed circuit explanation follows, reference being had to appropriate circuits.

The following operating characteristics will be described: (1) The method of obtaining the instantaneous percent magnetic iron; (2) the method of storing the accumulated magnetic iron and gross tonnages; (3) the method whereby a percent magnetic iron reading, determined by the accumulated tonnages, may be obtained,

when desired, through the use of the read out switch and (4) the method whereby, after a predetermined interval of time, the system automatically read out.and resets itself. Reference will generally be made to FIG. 2 unless otherwise indicated.

T he Instantaneous Reading of Percent Iran passing over the conveyor scale 27 (FIG. 1) likewise as explained previously. Points 184 on slidewire 104, and 185 on slidewire 109 are tied together and constitute the common lead 186 of the ratio circuit, designated, in

continuous ball and disc integrator 168 operates the counter 178 at a variable but continuous speed,'and not at a constant speed, intermittent operation as does the vane oscillator type integrator utilized in. themagnetic tonnage recorder 105. Theresult is the same, however, and, in this case counter 178 operates switch 209 which in turn energizes solenoid coil 210 through limit switches 206 and 207 and normally closed contact P The solenoil 210 armature in turn advances contactor 211 on rebroken line box 187. The variable voltage between points 103 and 184,and 164 and 185 pass through D.C. relay contacts R and R intothe ratio circuit. The field signals at points 188 and 189 are of like polarity and 0p poseeach other. The signal coming from the coil passes through series dropping resistor 190 and is impressed across 191. The gross tonnage signal is passed through series dropping resistor 192 and impressed across resistor capacitor network 193 and 194. Capacitor 195 and resistor 196 form a dampening circuit. The dilference of polarity between points 197 and 198 will determine the direction of balance motor 201 rotation. Forinstance: if point 198 is positive with respect to point 197, the balance motor will drive in one direction. This diiference of potential is fed to a suitable D.C. amplifier 165 similar to that shown in FIG. 4 and described previously, which in turn energizes winding 200 of the motor. The phase of this signal determines direction of rotation. motor, in turn, drives an indicator 26 which indicates the percent magnetic iron, and it also moves a contactor on The resistor 193. This resistor permits the system to achieve a null balance inasmuch as it will drive the balance motor until there is no difference of potential between points 197 and 198.

Storage of Information as to Percent Iran The storage of accumulated magnetic and gross tonnages is accomplished as follows: As can be seen from previous descriptions of circuit operations, the amount of magnetic material passing through coil 20 (FIG. 1) determines how long counter 203 (FIG; 2) operates in a specific time. A complete revolution of the counter shaft indicates the least amount of material, which in this case for read out and system reset is ten minutes.

. storage devices into the ratio instrument.

sistor 110 to store the accumulated gross tonnages.

To summarize at this point: two ten-turn 3600 poten- I tiometers 110 and 111 are advanced a specific angular movement by. two solenoids each energized by pulses from their respective counters. The rate at which they are pulsed is proportional to the amount of gross and magnetic material on the conveyor.

Reading Accumulated Information Without Resetting When it is desired to read the accumulated percent magnetic iron without resetting the system, switch B (also shown at 35 FIG. 1) is depressed and held closed long enough to obtain an accurate reading on ratio recorder 26. Depressing B results in applying 117 V. AC. to relay coil R which in turn breaks contacts R and R and closes contacts R and R This disconnects variable signals from slidewires 109 and 104 and applies the sig nal from storage 'slidewares 110 and 111 to the ratio circuit 187 and hence to the ratio indicator-recorder 26.

Timed Read-Out and Reset To provide automatic read on and rese', timer motor T at the end of a predetermined period mechanically breaks contact between 214 and 215 and makes contact between 216 and 217, which results indisconnecting power source from timer motor and applying power to program timer motor P. This motor through rotary cam action operates switches labeled P through P (as indicated by broken lines) for varying intervals of time and sequences. In this particular case, the total time taken Switch P is closed by the rotary cam for the entire period of time. This provides a maintaining circuit for programming motor P after switch S is returned to its normal position. After the elapsed period, this contact is opened by motor P and in turn de-energizes itself. P is opened momentarily at the very beginning of the reset period and results in de-energizing motor T and clutch T allowing the timer to reset to its zero position. Through spring action timer indicating. pointer is returned to zero and switches S and S are returned to their normal position. Shortly afterthe timer is reset, switch P is closed which applies power to timer and timing cycle starts again. P is closed shortly after P and is held in for a brief period. This energizes relay coil R which in turn opens relay contacts R and R and closes R and R This connects the After a brief a period, P opens andinterrupts the voltage to balance a main open until shortly before P is opened again. Dur

The other side L; of the 117v. A.C. line is connected to the solenoid coil 205 through normally closed contact P and through limit switches 206 and207. The operation of limit switches and P will later be explained when de- IStorage of Information .as to Gross Weight of Ore The storage of gross tonnages is accomplished in the exact manner as explained above except for a difference in the counter operator. As explained previously, the

motor 201 causing it to remain in position. R, will re ,ing the period that P is closed, P and Pr, are opened and P and P are closed. P opens up the counting circuit and therebyprevents solenoids 205 and 210 from advancing contactors 211- and 208 on their slidewires.

' Shortly after P isopened, P is closed energizing reset motor T and solenoids 218 and 219. Solenoids 218 and 219 move two gears. The gear responsive to solenoid 218 links the gross tonnage storage slidewire contactor 211 to the reset motor T The other solenoid 219, links the maggears from the counting mechanism. Since the above described resetting action takes a very short time, P is opened and P closed very soon after resetis complete, thereby completing a cycle and allowing the storage devices to begin storing the incoming information again.

Digital Recording of Accumulated Gross Tonnage Another feature of this invention, not yet described and associated with switches P and P is a device to record in digital form, the accumulated gross tonnage. This information will be stored until the system automatically times out or the reset switch is depressed, at which time the counter will reset to its zero position.

During the period that the storage devices are being reset by motor T P is open and P is closed thereby energizing the reset motor. At the same time that P is opened, P is also opened so that counter 224 cannot count during resetting action. Shortly after P is opened, P is closed causing solenoid 225 to be energized which in turn resets counter 224 to zero. To minimize error, shortly after reset action takes place, P is opened and P is closed which permits counter 224 to resume accumulating gross tonnages again.

The counter operates on low voltage DC. and has a fast resetting mechanism. The necessary voltage is developed by a DC. power supply utilizing step down transformer T containing a center tapped secondary. The two diodes 226 and 227 utilizing the center tap provide full wave rectification which is filtered by resistor-condenser network 228 and 229. The operating voltage is impressed across resistor 228 which in turn operates the counter. The counter operation is as follows: As shown in previous circuit descriptions for each pulse received from gross tonnage counter switch 209, solenoid 210 is energized through 207, 206 and P In parallel with these above stated components is relay coil R which is also energized each time switch 209 is closed. This relay coil causes contact 230 to close which applies power to solenoid 231 through P and the power supply. Each time 230 is closed, counter 224 is advanced one digit by solenoid 231.

Manual Reset If it is desired to reset the system manually, switch B (also shown as 36, FIG. 1) may be depressed which resets the timer and causes program motor P to go through same read out and resetting operation as just described. Momentarily depressing switch B permits relay coil S to be energized, which closes holding contact 232 and program motor contact 233. This will then permit the system to go through normal read out and reset. Relay coil S will be de-energized when P is opened.

What is claimed is:

1. Apparatus of the character described for. instan-. taneously and automatically assaying the amount and the relative proportions of magnetic and non-magnetic fractions of a ferrous metal ore when said ore is moving on a conveyor past a measuring zone, said apparatus comprising sensing means at said measuring zone responsive to variations in quantity of said magnetic fractions, a scale in operative contact with said conveyor at said measuring zone and responsive to total weight of ore passing said measuring zone on said conveyor, a ratio indicator adapted to show and record the percentage of magnetic fraction with relation to the total weight of ore, means establishing an operative connection between said sensing means and said ratio indicator whereby said ratio indicator receives a first signal proportional to the amount of magnetic fraction passing said measuring zone, and other means establishing an operative connection between said scale and said ratio indicator whereby said ratio indicator receives a second signal proportional to the total amount of ore passing said measuring zone.

2. Apparatus of the character described for instantaneously and automatically assaying the amount and the I 2" relative proportions of magnetic and non-magnetlc fractions of aferrousmetal or when said'ore is moving on a conveyor past a measuring zone, said apparatus comprising sensing means at said measuring zone responsive to variations in quantity of said magnetic fraction, a scale in operative contact with said conveyor at said measuring zone and responsive to total weight of ore passing said measuring zone on said conveyor, a ratio indicator adapted to show and record the percentage of magnetic fraction with relation to the total weight of ore, means establishing an operative connection between said sensing means and said ratio indicator whereby said ratio indicator receives a first signal proportional to the amount of magnetic fraction passing said measuring zone, other means establishing an operative connection between said scale and said ratio indicator whereby said ratio indicator receives a second signal proportional to the total amount of ore passing said measuring zone, and means operatively responsive to said first signal, and adapted to indicate the total weight of said magnetic fraction passing said measuring zone.

3. Apparatus of the character described for instantaneously and automatically assaying the amount and the relative proportions of magnetic and non-magnetic fractions of a ferrous metal ore when said ore is moving on a conveyor past a measuring zone, said apparatus comprising sensing means at said measuring zone responsive to variations in quantity of said magnetic fraction, a scale in operative contact with said conveyor at said measuring zone and responsive to total weight of ore passing said measuring zone on said conveyor, a ratio indicator adapted to show and record the percentage of magnetic fraction with relation to the total weight of ore, means establishing an operative connection between said sensing means and said ratio indicator whereby said ratio indicator receives a first signal proportional to the amount of magnetic fraction passing said measuring zone, other means establishing an operative connection between 'said scale and said ratio indicator whereby said ratio indicator receives a second signal proportional tothe total amount of ore passing said measuring zone, and means operatively responsive to said second signal, and adapted to indicate the total weight of ore passing said measuring zone.

4. Apparatus of the character described for automatically assaying the amount and the relative proportions of magnetic and non-magnetic fractions of a ferrous metal ore when said ore is moving on a conveyor past a measuring zone, said apparatus comprising sensing means at said measuring zone responsive to variations in quantity of said magnetic fraction, a scale in operative contact with said conveyor at said measuring zone and responsive to total weight of, ore passing said measuring zone on said conveyor, a ratio indicator adapted to show and record the percentage of magnetic fraction with relation to the total weight of ore, means establishing an opera tive connection between said sensing means and said ratio indicator whereby said ratio indicator receives a first signal proportional to the amount of magnetic fraction passing said measuring zone, other means establishing an operative connection between said scale and said ratio indicator whereby said ratio indicator receives a second signal proportional to the total amount of ore passing said measuring zone, and means operatively responsive to said first signal and adapted to incrementally accumulate and indicate the total weight of magnetic fraction which has passed said measuring zone in a predetermined time period.

5. Apparatus of the character described for automatically assaying the amount and. the relative proportions of magnetic and non-magnetic fractions of a ferrous metal ore when said ore is moving on a conveyor past a measuring zone, said apparatus comprising sensing means at said measuring zone repsonsive to variations in quantity of said magnetic fraction, a scale in operative contact with said conveyor at said measuring zone and responmagnetic fraction at I 13 sive to total weight of ore passing said measuring zone on said conveyor, a ratio indicator adapted to show and record the percentage of magnetic fraction with relation to the total weight of ore, means establishing an operative connection between said sensing means and said ratio indicator whereby said ratio indicator receives a first signal proportional to the amount of magnetic fraction passing said measuring Zone, means operatively responportional to the totalamount of ore passing said measursive to said first signal and adapted to accumulate and I indicate the amount of magnetic fraction, other means establishing an operative connection between said scale and said ratio indicator whereby said ratio indicatorreceives a second signal proportional to the total amount of ore passing said measuring Zone, and meansoperatively responsive to said second signal and adapted to accumulate and indicate the total weight of ore which has passed said measuring zone in a predetermined period of time.

6. Apparatus of the character described for automatically assaying the amount and the relative proportions of magnetic and non-magnetic fractions of a. ferrous metal ore when said ore is moving on a conveyor past a measuring zone, said apparatus comprising sensing means at saidimeasuringzone responsive to variations in quantity of said magnetic fraction, a scalegin operativecontact With said conveyor at said measuring zone and responsive to total weight of ore passingsaid measuring zone on said conveyor, a ratio indicator adapted to show and record the percentage of magnetic fraction with relation to the total weight of ore, meansestablishing an operative connection between said sensing means and said ratio indicator whereby said ratio indicator receives a first signal proportional to the amount of magnetic fraction passing said measuring zone, other means establishing an operative connection between said scale and said ratio indicator whereby said ratio indicator receives a second signal proportional to the total amount of ore passing said measuring zone, means responsive to said first signal and adapted to accumulate and indicate the total weight of said magnetic fraction which has passed said measuring zone in a predetermined period of time, and further means responsive to said second signal and adapted to accumulate and indicate the total weight of ore which has passed said measuring zone in the said predetermined period of time.

tion at the end of said predetermined time period.

9. Apparatus as defined in claim 5 including, in combination therewith, means to automatically reset to zero the means for accumulating and indicating the amount of the end of said predetermined time period. g

10. Apparatus of the character described for automatimagnetic and non-magnetic fractions of a ferrous metal ore when said ore is moving on a conveyor past a measof said magnetic fraction, a scale in operative contact with said conveyor at said measuring zone and. responsive to total weight ofore passing said measuring zone on said conveyor, a ratio indicator adapted to show ,and record ,cally assaying the amount and the relative proportions of the percentage of magnetic fraction with relatio rTYEi the total Weight of-ore, means establishing'an operative connection between said sensing means and said ratio indicator whereby said ratio indicator receives a first signal proportional to the amount of magnetic fraction passing said measuring zone, other means establishing an operative connection between said scaleand said ratio indicator whereby said ratio indicator receives a second signal pro ing zone, and means operativelyassociated with said ratio indicator for automatically computing, indicating, and re-v electrical current in the secondary constituting a first signaLa second sensing means comprising a scale and a strain gauge at said measuring zone responsive to variations in total Weight of said ore and adapted to .produce a second signal proportional to variations in such weight, speed-sensitive means responsive to variations in rate of movement of said conveyor, integrating means responsive to said second signal and to said speed sensitive means and adapted to operate a counter indicating the actual Weight of ore passing said measuring zone, and a ratio indicator adapted to receive said first signal from said first sensing means and a signal from said integrating means and to correlate said last named two signals and to assay, indicate and record the percentage of said magnetic fraction in said ore. s

p 12. Apparatus as defined in claim 11 and wherein there is provided a multi-turn potentiometer adapted to receive and automatically accumulate a succession of impulses proportional to unit increments of magnetic fraction passing said measuring zone, and to indicate the total amount of such magnetic fraction accumulated over any selected period.

13. Apparatus as defined in claim 12 wherein there is provided means for automatically resetting said potentiometer to a zero, re-starting condition at the end of such selected period. 7 p p 14. Apparatus as defined in claim 11 and wherein therein is provided a multi-turn potentiometer adaptedto receive and automatically accumulate a succession of impulses proportional to unit increments of weight of ore passing said measuring zone, and to indicate the total weight ofsuch ore accumulated over any preselected period. j

15. Apparatus as defined in claim 14 wherein there is provided means for automatically resetting said potentiometer to a zero, restarting condition at the end of such selected period.

16. Apparatus of the character described for instantaneously and automatically assaying the amount and the relative proportions of magnetic and non-nagnetic fractions of a ferrous metal ore which has moved on a conveyor past a measuring zone within a predetermined period, said apparatus comprising sensing means at said measuring zone responsive to variations in quantity of said'magnetic fraction, a scale in operative contact with said conveyor at said measuring zone and responsive to total weight of ore which haspassed said measuring zone'on said conveyor, a ratio indicator adapted to show nal, and adapted to indicate the total weight of said magnetic fraction which has passed said measuring zone,

17. Apparatus of the characterdescribed for automatically assaying the amount and the relative proportions of magnetic and non-magnetic fractions of a ferrous metal ore which has moved on a conveyor past a measuring zone within a predetermined period, said apparatus comprising sensing means at said measuring zone responsive to variations in quantity of said magnetic fraction, a scale in operative contact with said conveyor at said measuring zone and responsive to total Weight of ore which has passed said measuring zone on said conveyor, a ratio indicator adapted to show and record the percentage of magnetic fraction with relation to the total Weight of ore within said period, means establishing an operative connection between said sensing means and said ratio indicator whereby said ratio indicator receives a first signal proportional to the amount of magnetic fraction which has passed said measuring zone, other means establishing an operative connection be tween said scale and said ratio indicator whereby said ratio indicator receives a second signal proportional to the total amount of ore which has passed said measuring zone, and means operatively responsive to said first signal and adapted to incrementally accumulate and indicate the total weight of magnetic fraction which has passed said measuring zone in said predetermined period.

18. Apparatus of the character described for automatically assaying the amount and the relative proportion of magnetic and non-magnetic fractions of a terrous metal ore when said ore has moved on a conveyor past a measuring zone, said apparatus comprising sensing means at said measuring zone responsive to variations in quantity of said magnetic fraction, a scale in operative contact with said conveyor at said measuring zone and responsive to total weight of ore which has passed said measuring zone on said conveyor within a predetermined period, a ratio indicator adapted to show and record the percentage of magnetic fraction with relation to the total weight of ore, means establishing an operative connection between said sensing means and said ratio indicator whereby said ratio indicator receives a first signal proportional to the amount of magnetic fraction which has passed said measuring zone, means operatively responsive to said first signal and adapted to accumulate and indicate the amount of magnetic fraction, other means establishing an operative connection between said scale and said ratio indicator whereby said ratio indicator receives a second signal proportional to the total amount of ore which has passed said measuring zone, and means operatively responsive to said second signal and adapted to accumulate and indicate the total weight of ore which has passed said measuring zone in said predetermined period.

19. Apparatus of the character described for automatically assaying the amount and the relative proportions of magnetic and non-magnetic fractions of a ferrous metal ore when said ore has moved on a conveyor past a measuring zone, said apparatus comprising sensing means at said measuring zone responsive to variations in quantity of said magnetic fraction, a scale in operative contact with said conveyor at said measuring zone and responsive -to total weight of ore which has passed said measuring zone on said conveyor within a predetermined time period, a ratio indicator adapted to show and record the percentage of magnetic fraction with relation to the total Weight of ore, means establishing an operative connection between said sensing means and said ratio indicator whereby said ratio indicator receives a which has passed said measuring zone in said predetermined period of time, and further means responsive to said second signal and adapted to accumulate and indicate the total weight of ore which has passed said measuring zone in the said predetermined period of time.

20. Apparatus of the character described in claim 19 wherein means is provided for recording both the total accumulated weight of said magnetic fraction and the total accumulated weight of said ore.

21. Apparatus as defined in claim 17 wherein means is provided to automatically re-set to zero the means for accumulating and indicating the amount of magnetic fraction at the end of said predetermined time period.

22. Apparatus as defined in claim 18 including, in combination therewith, means to automatically re-set to zero the means for accumulating and indicating the amount of magnetic fraction at the end of said prede termined time period.

23. Apparatus of the character described for automatically assaying the amount and the relative proportions of magnetic and non-magnetic fractions of a ferrous metal ore which has passed over a conveyor past a measuring zone, within a preselected period of time, said apparatus comprising sensing means at said measuring zone responsive to variations in quantity of said magnetic fraction, a scale in operative contact with said conveyor at said measuring zone and responsive to total weight of ore which has passed said measuring zone on said conveyor within said period, a ratio indicator adapted to show and record the percentage of magnetic fraction with relation to the total Weight of ore, means establishing an operative connection between said sensing means and said ratio indicator whereby said ratio indicator receives a first signal proportional to the amount of magnetic fraction which has passed said measuring zone, other means establishing an operative connection between said scale and said ratio indicator whereby said ratio indicator receives a second signal proportional to the total amount of ore which has passed said measuring zone, and means operatively associated with said ratio indicator for automatically computing, indicating, and recording the average assay of the ore which has passed said measuring zone over said preselected elapsed period.

24. Apparatus of the character described for automatically assaying the amount and the relative proportions of magnetic and non-magnetic fractions of a ferrous metal ore when said ore has moved on a conveyor past a measuring zone, said apparatus comprising a first sensing means at said measuring zone responsive to variations in quantity of said magnetic fraction and consisting of a primary-secondary induction couple adapted to produce a varying electrical current in the secondary constituting a first signal, a second sensing means comprising a scale and a strain gauge at said measuring zone responsive to variations in total Weight of said ore and adapted to produce a second signal proportional to variations in such weight, speed-sensitive means responsive to variations in rate of movement of said conveyor, integrating means responsive to said second signal and to said speed sensitive means and adapted to operate a counter indicating the actual weight of ore which has passed said measuring zone in a preselected time period, and a ratio indicator adapted to receive said first signal from said first sensing means and a signal from said integrating means and to correlate said last named two signals and to assay, indicate and record the percentage of said magnetic fraction in said ore which has passed said measuring zone in said time period.

25. Apparatus as defined in claim 24 and wherein there is provided a multi-turn potentiometer adapted to receive and automatically accumulate a succession of impulses proportional to unit increments of magnetic fraction passing said measuring zone, and to indicate the total amount of such magnetic fraction accumulated over said time period.

26. Apparatus as defined in claim 25 wherein there 28. Apparatus as defined in 'claim 27 wherein there is provided means for automatically resetting saidpois provided means for automatically resetting said potentiometer to a zero, re-starting condition at the end tentiorneter to a zero, restarting condition at the end of such time period. of such time period.

27. Apparatus as defined in claim 24 and wherein 5 there is provided a multi-turn potentiometer adapted References Cited in the file of this Patent to receive and automatically accumulate a succession UNITED STATES PATENTS of impulses proportional to unit increments of weight 7 0 7 9 Onstad Aug. 3 195 of ore passing said measuring zone, and to indicate the 2,753 629 l O 30 1956 total weight of such are accumulated over said time 10 2,888,026 Henderson et a1. May 26, 1959 period. 2,940,040 Rosenthal June 7, 1960 

1. APPARATUS OF THE CHARACTER DESCRIBED FOR INSTANTANEOUSLY AND AUTOMATICALLY ASSAYING THE AMOUNT AND THE RELATIVE PROPORTIONS OF MAGNETIC AND NON-MAGNETIC FRACTIONS OF A FERROUS METAL ORE WHEN SAID ORE IS MOVING ON A CONVEYOR PAST A MEASURING ZONE, SAID APPARATUS COMPRISING SENSING MEANS AT SAID MEASURING ZONE RESPONSIVE TO VARIATIONS IN QUANTITY OF SAID MAGNETIC FRACTIONS, A SCALE IN OPERATIVE CONTACT WITH SAID CONVEYOR AT SAID MEASURING ZONE AND RESPONSIVE TO TOTAL WEIGHT OF ORE PASSING SAID MEASURING ZONE ON SAID CONVEYOR, A RATIO INDICATOR ADAPTED TO SHOW AND RECORD THE PERCENTAGE OF MAGNETIC FRACTIN WITH RELATION TO THE TOTAL WEIGHT OF ORE, MEANS ESTABLISHING AN OPERATIVE CONNECTION BETWEEN SAID SENSING MEANS AND SAID RATIO INDICATOR WHEREBY SAID RATIO INDICATOR RECEIVES A FIRST SIGNAL PROPORTIONAL TO THE AMOUNT OF MAGNETIC FRACTION PASSING SAID MEASURING ZONE, AND OTHER MEANS ESTABLISHING AN OPERATIVE CONNECTION BETWEEN SAID SCALE AND SAID RATIO INDICATOR WHEREBY SAID RATIO INDICATOR RECEIVES A SECOND SIGNAL PROPORTIONAL TO THE TOTAL AMOUNT OF ORE PASSING SAID MEASURING ZONE. 